Sources of timulus control during multiple discriminations.
Even 'smart' discrimination boils down to the exact cue that was last reinforced.
01Research in Context
What this study did
Zeiler (1968) ran size-discrimination sessions with pigeons. Birds saw two circles in a row and had to peck the larger one.
During probe trials the experimenter sneaked in new sizes. The team watched which sizes the birds still pecked.
What they found
The pigeons pecked the key that matched the absolute size they had been reinforced for. They did not follow a 'pick the bigger one' rule.
Recent rewards, not abstract relations, controlled every choice.
How this fits with other research
Tracey et al. (1974) extends the idea. They showed pigeons compound cues and found distinctive parts won the race for control, just like absolute size did here.
Zentall et al. (1975) looks like a contradiction. They presented common and distinctive features at the same time and saw no clear winner. The fight fades because they used simultaneous cues, while Zeiler (1968) and Tracey et al. (1974) used successive cues. Change the layout, change the outcome.
Siegel et al. (1970) replicates the spirit. Pigeons learned a 'person-present' concept under both successive and simultaneous setups without any fancy relational reasoning, backing the plain-stimulus-control story.
Why it matters
Before you say a client 'understands the concept,' probe with fresh stimuli. If the learner picks the same absolute cue that earned reinforcement before, you are seeing stimulus history, not a concept. Design your teaching sets so the critical feature stands alone and keep notes on what was last reinforced. That tiny check saves you from over-hyping abstract understanding and keeps your program grounded in basic stimulus control.
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02At a glance
03Original abstract
Pigeons learned to respond to the middle-sized member of six or seven sets of three stimuli differing in size. The sets were used successively, each serving as the discrimination problem from 10 to 16 times. After attaining criterion with one set, the birds received the others as probes. The number of responses in probes was related to the similarity of the probes to the prevailing discrimination problem. The birds responded either to the probe stimulus to which responding had most recently been reinforced, or to the probe stimulus closest in size to the positive member (S+) of the prevailing discrimination problem. Responses to a middle-sized probe-set stimulus occurred when it was the probe-set member most recently correlated with reinforcement, when it was one of two stimuli closest in size to S+, and when the stimulus closest in size to S+ was a negative member of the discrimination problem. All of the behavior could be explained in terms of control by the absolute sizes of the various stimuli.
Journal of the experimental analysis of behavior, 1968 · doi:10.1901/jeab.1968.11-549